The feedback of test and inspection results data is of critical importance for process diagnostics and increasing yield in a semiconductor manufacturing line. To be most effective, data relating to a particular semiconductor device must always be traceable to that devices lot, wafer within the lot and location on the specific wafer. However, once wafers are tested and the good die removed, the ability to maintain traceability of each of the individual die, throughout the remainder of the process, is an extremely difficult task that has, in the past, required manual intervention.
Previous approaches for associating data with devices during the semiconductor manufacturing process have included the following two methods:
1) Paper travelers are attached to device carriers, which are then hand carried through the process and the paper traveler manually updated at each step; and PA1 2) Individual device lead frames and packages are marked with a unique serial number as soon as the chip is installed, the serial number may be read at each processing step and the results manually, or automatically, recorded after which the device is re-marked before shipment. Such a mark might be a two-dimensional array similar to a bar code.
The first method is inherently unreliable, relying as it does on manual recording of information, and is prone to error or improper use. The paper travelers are easily detached from the carriers or lost in the manufacturing process. The second method requires additional steps in the manufacturing process and does not provide a solution for devices that are sold as bare die.
The use of electronic memory devices is well known in many applications. In particular, the use of such devices in the form of semiconductor integrated circuits (ICs) embedded in cards for carrying financial or other information has increased in recent years. Such cards, being of the same size and shape as magnetic stripe cards such as those used for credit cards or the like, have an integrated circuit embedded within the body of the card and some means for the IC to communicate with a reader so as to exchange data. In their simplest form, IC cards or "smart cards" as they are known, include a simple memory device which provides information to a reader on demand. More sophisticated devices also allow data to be written to the memory and can even perform basic data processing in the card itself. The card reader and or read/write device contacts the IC via electrical contacts on the surface of the card ("contact") or via an r.f. inductive link, there being an inductive loop formed inside the card which can provide power to the IC and send and receive data passed between the IC and read/write device ("contactless"). The technology required to perform these activities is well known and a summary of this can be found in the article "Smart Cards" by Carol H. Fancher published in Scientific American, August 1996, Vol. 275, No. 2, pp 40-45.
The present invention resides in the realization that the integration of "smart card" technology into the semiconductor manufacturing process can not only overcome the problems described above, but can also provide information in sufficient quantity and at appropriate times to allow better management of the manufacturing process.
It is an object of the present invention to provide a system in which such integration can be realized.